Applicants began collecting the forms on Saturday, and 100,000 of those have been distributed in the Muslim holy city of Makka, newspapers said.
Media reports said scores of Yemenis and Egyptians have been collecting applications from the civil status office in the capital Riyadh.
Not for Palestinians?
Some Palestinians also queued to get applications, despite an Arab League ban on naturalising Palestinian refugees in Arab
Applications can be presented starting 23 May, according to an official in the civil status department.
Unofficial estimates put at one million the number of residents potentially eligible for citizenship of the kingdom, where there are more than six million expatriates, mostly Asian, out of a population of 22.6 million.
The rush for applications comes despite the fact that an amended naturalisation law approved by the Saudi cabinet last October makes it tougher for permanent residents to acquire Saudi citizenship.
Tough eligability rules
The amendments to the nearly 50-year-old legislation, which were proposed by the Shura (consultative) Council in May 2004, require a resident to have lived permanently in Saudi Arabia for 10 years before qualifying to apply for citizenship under certain conditions.
The Shura Council decided to
increase citizenships in 2004
This doubled the previous requirement of five years of permanent residence.
In most cases, the applicant must also have a profession "which the country needs".
The Interior Ministry has also set up a system of points to eventually grant citizenship, requiring an applicant to score at least 23 points to qualify.
Interior Ministry's decision
In addition, an applicant must present certification from the preacher of his local mosque to confirm he regularly attends the Muslim place of worship.
The tough regulations have left many potential applicants without high hopes of success, say critics.
The decision to grant citizenship will ultimately lie with the interior minister.